1. Technical Field
The present invention relates generally to vehicle fuel systems, and more particularly, concerns a fuel injection system for gaseous-fueled internal combustion engines.
2. Background
Alternative fuel systems have become an ever-greater concern in the search to conserve energy and emission control. The development of alternative energy sources for use in automotive vehicles is a goal of automobile manufacturers. The alternative energy sources must provide the required power needed to operate the vehicle, and at the same time be energy efficient, reduce emissions, and be cost effective. One such alternative energy source under consideration is a hydrogen-fueled internal combustion engine. Natural gas has also long been considered an alternative fuel for internal combustion engines.
A problem with using gaseous fuels for part injection engines such as natural gas or hydrogen, however, is reduced power output when compared to liquid fuel such as gasoline due mostly to the loss in volumetric efficiency. For example, in the case of natural gas, the proportion of the volume of the fuel/air mixture occupied by the fuel is approximately 10%. In the case of hydrogen, the proportion of the volume of the fuel/air mixture occupied by the fuel is approximately 30% at stoichiometry. In contrast, in liquid-fueled engines, the proportion of the volume of the fuel/air mixture occupied by the fuel is approximately 1.5%. Thus, for gaseous-fueled engines, the proportion of intake air in the fuel/air mixture decreases by an amount corresponding to the increase in the volume of the fuel component. As compared to a gasoline engine or a diesel engine, the amount of intake air decreases and the volumetric efficiency and the engine output decreases as well. To increase the volumetric efficiency, a larger quantity of fresh air must be inducted into the engine cylinders for a given quantity of fuel injected. Thus, there exists a need for gaseous-fuel injection systems which result in improved engine volumetric efficiency.
In the present invention, the aforementioned problem is solved through the provision of a novel gaseous fuel injection system whereby gaseous fuel is injected at a high velocity along the periphery of the intake port thereby creating a local lower pressure central core which in turn increases the overall intake charge flow and, hence, volumetric efficiency of the engine. The high pressure gaseous fuel is directed by guide tubes or formations in the intake port along the walls of the intake port, toward the intake valve opening and, in a preferred embodiment, is injected after the start of induction.
In one embodiment, a fuel injection system for a gaseous-fueled engine is provided. The engine comprises a plurality of cylinders each defining a combustion chamber and associated with at least one intake port in fluid communication with an intake manifold and separated from the combustion chamber by an intake valve operable between an open and closed position. The fuel injection system comprises at least one gaseous fuel injector for each of the engine cylinders, wherein each fuel injector is located proximate the intake manifold. A guide tube connects each of the gaseous fuel injectors to at least one of the intake ports. The guide tube comprises a fluid passage arranged within the respective intake port substantially tangent and adjacent to an interior wall of the intake port and directed toward the respective intake valve. The guide tube is adapted to deliver high-pressure gaseous fuel from the injector to the respective cylinder along the interior wall of the intake port. In this way, the high velocity peripheral fuel charge creates a lower pressure central core within the intake port which, in turn, increases the overall intake charge flow and engine volumetric efficiency.
An advantage of the present invention is that it improves the volumetric efficiency of gaseous-fueled internal combustion engines. Other advantages of the invention will become apparent reading the following detailed description and appended claims, and upon reference of the accompanying drawings.